Method and composition for treating steel



Patented July 14, 1942 METHOD AND coMrosmoN roa mean we s'mm.

Clarence E. Mange, St. Louis, Mo., asslgnor to Jackes-EvansManufacturing Company,

Louis, M o., a corporation of Missouri No Drawing. Application March 21,1941, Serial Claims.

- The present invention relates to methods and compositions for treatingsteel, andinore particularly to methods and compositions for obtaining ablack surface upon the steel.

Among the objects of this invention are the provision of methods andcompositions for surface-treating steel articles; the provision ofmethods and compositions for surface-treating steel articles to form asurface which is heatresisting even at high temperatures; the provisionof methods and compositions for obtaining a surface which isrust-resistant, and which yields without cracking to even sharp bendingof the article; and the provision of methods and compositions fortreating steel articles to obtain a uniform and pleasing black surfacethereupon. Other objects will be in part obvious and in part pointed outhereinafter.

The invention accordingly comprises the ingredients and combinations ofingredients, the proportions thereof, steps and sequence of steps, andfeatures of composition and manipulation, which will be exemplified inthe products and methods hereinafter described, and the scope of theapplication of which will be indicated in ,the following claims.

Steel articles are strong and durable, but their surface characteristicsare not all that could be desired. More pleasing colors are frequentlywanted, and steel articles favor the formation of rust inthe presence ofwater. It has become the practice therefore to coat the surface of sucharticles with various protective agents, and/or decorative means. Whileuseful results have in general been obtained by suchpractices, they areimpractical for certain applications, and in some cases the cost ofapplication and/or subsequent treatment is excessive. I

The present invention provides improved methods and compositions forimparting an attractive flexible black surface to steel articles, whichsurface is rust-resistant, and very tenaciously adherent to the steelarticle. Moreover, the coating is resistant to heat, and the coatedarticle may be subject to temperature as high as red heat, or evenhigher, without deleteriously affecting the coating. Where lacquer orthe like, for example, is employed, it is necessary to protect'the steelarticle from even moderate heat, and the application of any temperatureanalogous to a red heat would quickly burn away the surface coating,usually leaving an unattractive carbon residue.

According to the present invention, a solution of a plurality ofingredients either in water, in

an organic solvent, or in a combination of several such solvents, isformed. These ingredients comprise a lithium compound, a compound of analkali metal other than lithium, and an alkali. For certainapplications, it is preferable that an acid radical likewise be presentalthough this is not essential. For most purposes, it is preferable thata single compound be employed to act in more than one capacity. Thus,the lithium compound may likewise contain an acid radical, while thecompound of the other alkali metal may likewise be an alkali, or viceversa. For example, lithium acetate is both a lithium compound andcontains an acid radical. It performs both functions in the compositionsemployed in the present invention. Similarly, sodium hydroxideis both acompound of an alkali metal other? than lithium, and an alkali, and itperforms/the functions of both in the present invention.

Any soluble lithium compound may be employed. For example, lithiumhydroxide, lithium nitrite, lithium acetate, or the like.

The compound of the alkali metal other than lithium may be, for example,sodium hydroxide. potassium hydroxide, sodium acetate, sodium nitrate,sodium nitrite, or the like.

The acid radical should preferably be one which breaks down, or whichreadily volatilizes Among these may be mentioned the nitrates, thenitrites, the acetates, or the like. Hydroxides and cyanides may beemployed, provided they are in relatively low concentrations, sincethey};

do not readily volatilize.

The alkali referred to above may be either a material which is alkalinein reaction, such as a hydroxide, or it may be an alkali former, such asan acetate, which forms an alkali at the temperature of reaction.Throughout the specification and claims it will be understood thatalkali formers are included when alkalis or hydroxides are referred to.

As has been pointed out previously, more than one of these functions maybe combined in the same chemical compound.

The solvent employed may be water or an organic solvent capable ofdissolving a sufficient concentration of the active ingredients referredto. Methyl alcohol, ethyl alcohol, isopropyl alcohol and ethyl acetate,for example, may be employed either alone or in admixture with eachother and/or with water. The preferred solvent is, however, a mixture ofwater and isopropyl alcohol.

For most purposes, it is preferable to add to the solvent 9.; smallproportion of a wetting agent. This is especially true where the steelarticles have not been de-greased. Wetting agents in general have abeneficial effect, but the preferred agent is a sulfonated ether, suchas the compound marketed by Rohm and Haas Company under the name ofTriton 720." Only a relatively small proportion of the wetting agentneed be present. It will be found that a proportion of approximatelone-fifth or onefourth of one per cent. is sufllcient. Largerproportions are in general undesirable, while smaller proportions affordonly partially improved results.

The following examples illustrate several of the possible compositionsfor treating steel in accordance with the present invention. They areexemplary only:

Example 1 Lithium hydroxide g 1.72 Sodium nitrate g .15 Sodium acetate g.22 Sodium nitrite g .12 Water ml 60 Isopropyl alcohol ml 40 Sulfonatedether (Triton 720) ml .2

Example 2 Sodium acetate g .32 Lithium hydroxide g 2.1 Water ml 36Isopropyl alcohol ml 64 Sulfonated ether ml .21

Example 3 Sodium hydroxide g .4 Lithium hydroxide g 2.0 Isopropylalcohol ml 57.5 Water ml 42.5 Sulfonated ether ml .25

Example 4 Lithium hydroxide g .49 Sodium hydroxide g .89 Water ml 50Example 5 Lithium hydroxide g 2 Sodium hydrovide g .49 Water ml 100Example 6 Grams Sodium hydroxide .4 Lithium hydroxide 2.0 Isopropylalcohol 57.5 Water 42.5 Sulfonated ether .25 I Example 7 1 GramsPotassium hydroxide .4 Lithium hydroxide 2.0 Isopropyl alcohol 57.5,Water 42.5

Sulfonated ether .25

In general, it is preferred that the lithium compound or salt shall bein substantially greater concentration than the compound or salt of theother alkali metal.

It is likewise preferred that the concentration of ingredients dissolvedin the solvent shall not exceed substantially five per cent. However,concentrations up to ten per cent., or even higher, may be employedunder certain circumstances. The dissolved ingredients, however, shouldnot be in sufficient concentration so that when the reaction with thesteel is subsequently carried out an impervious surface layer of moltensalts is formed. Such an impervious surface layer inhibits the reactionwith the steel surface described subsequently.

The above solutions maybe applied to the steel articles in anyconvenient manner. The articles may be dipped therein and withdrawn,leaving the solution adhering to the article, or the solution may bebrushed or sprayed on the article, or, where steel sheets are beingtreated, the sheets may merely be passed between rolls which have beenmoistened with the solution. The only requirement is that the solutionshall be relatively evenly distributed over and shall wet the surface ofthe article.

The solution having been applied to the surface of the article, thearticle is next heated to and maintained at a temperature sufficientlyhigh to carry out the reaction of the solution with the steel. Thistemperature may be, for example, 800 F., although this figure is in noway critical. Lower temperatures may be employed, although in general alonger period of time is then required. The only essential factor isthat the reaction between the solution and the steel surface shallproceed to form a uniform black surface.

It will be found that upon heating the steel article to, for example,800 F. the solution reacts with the steel surface and a uniform jetblacksurface is formed thereon. This surface is both rust-resistant andresistant to abrasion. Where a solution such as typified by Example 1 isemployed, the finished article may be crimped or otherwise worked atwill, and the surface will remain substantially intact.

Moreover, the finish remains black after the article has been heated tored heat, or even higher. The only result of such heating is to obtainunder certain circumstances a slight darkening of the finish, due tofurther reaction of the steel with the coating ingredients. On

the other hand, linseed oil base finishes, for example, would carburizeand burn oil long before an article coated with them reached red heat.

It is important that the entire surface of the steel article be wettedwith the solution since only the wetted portions can react. Accordingly,where water alone is the solvent employed, it is preferable that thesteel articles be de-greased to obtain a uniform and effective wettingof the surface.

The steel articles to be treated are preferably clean-finished, sincethe present treatment is not an effective method for removing scale orother impurities from the surface thereof.

Wetting agents in general may be employed to obtain improved wetting ofthe surface of. the steel article. However, the wetting agent should notcarburize, and preferably retains its wetting properties up to the pointat which the solvent begins to evaporate.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above products and methods withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

What is claimed is: 1. The method of treating steel which com- "prisesapplying to the surface of said steel a .solution comprising lithiumhydroxide, sodium nitrate, sodium acetate, and sodium nitrite in amixture of water and isopropyl alcohol, and heating the surface to asufliciently high temperature to react the steel and solution.

3. The method of treating steel which comprises applying to the surfaceof said steel a solution comprising lithium hydroxide, sodium nitrate,sodium acetate, and sodium nitrite in a mixture of water, isopropylalcohol and a sulfonated ether, and heating the surface to a sumcientlyhigh temperature to react the steel and solution.

4. A solution for treating steel comprising lithium hydroxide, sodiumnitrate, sodium acetate, and sodium nitrite in water and isopropylalcohol.

5. A solution for treating steel comprising lithium hydroxide, sodiumnitrate, sodium acetate, and sodium nitrite in water, isopropyl alcohol,and a sulfonated ether.

6. A solution for treating steel comprising lithium hydroxide, sodiumnitrate, sodium acetate and sodium nitrite in water and isopropylalcohol, the concentration of said salts being not substantially greaterthan ten per cent.

'7. The method of treating steel which comprises applying to the surfaceof said steel .a hydroxyl-containing solution comprising a lithium saltand the salt of an alkali metal other than lithium; any non-hydroxylanions present being members of the class consisting of acetates,nitrates, and nitrites; said solution containing not over 10% of solidsalts of which at least 4/10 of 1% and not over 2% is a lithium salt;the hydroxyl content being at least stoichiometrically equal to thelithium ion content; the content of the alkali metal other than lithiumbeing equal in weight to at least 1/5 of the lithium salt and not overtwice the lithium salt; and heating the surface of the steel to reactthe steel and salts is absence of a solvent. I

8. The method of treating steel which comprises applying to the surfaceof said steel a hydroxyl-containing solution comprising a lithium saltand the salt of an alkali metal other than lithium; any non-hydroxylanions present being members of the class consisting of acetates,nitrates, and nitrites; said solution containing not over 10% of solidsalts of which at least 4/ 10 of 1% and not over 2% is a lithium salt;the hyhydroxyl content being at least stoichiometrically equal to thelithium ion content; the content of the alkali metal other than lithiumbeing equal in weight to at least l/5 of the lithium salt and not overtwice the lithium salt; and heating the surface of the steel to reactthe steel and salts in absence of a solvent; said reaction beingconducted at approximately, 800 F.

9. The method of treating steel which comprises applying to the surfaceof said steel a hydroxyl-containing solution comprising a lithium saltand the salt of an alkali metal other than lithium; any non-hydroxylanions present being acetates; said solution containing not over 10% ofsolid salts of which at least 4/10 of 1% and not over 2% is a lithiumsalt; the hydroxyl content being at least stoichiometrically equal tothe lithium ion content; the content of the alkali metal other thanlithium being equal in weight to at least 1/5 of the lithium salt andnot over twice the lithium salt; and heating the surface of the steel toreact the steel and salts in absence of a solvent; said reaction beingconducted at approximately 800% F.

10. The method of treating steel which comprises applying to the surfaceof said steel a hydroxyl-containing solution comprising a lithium saltand the salt of an alkali metal other than lithium; any non-hydroxylanions present being nitrates; said solution containing not over 10% ofsolid salts of which at least of 1% and not over 2% is a lithium salt;the hydroxyl content being at least stoichiometrically equal to thelithium ion content; the content of the alkali metal other than lithiumbeing equal in weight to at least of the lithium salt and not over twicethe lithium salt; and heating the surface of the steel to react thesteel and salts in absence of a solvent; said reaction being conductedat ap-' proximately 800 F.

11, The method of treating steel which comprises applying to the surfaceof said steel a hydroxyl-containing solution comprising a lithium saltand the salt of an alkali metal other than lithium; any non-hydroxylanions present being nitrites; said solution containing not over 10% ofsolid salts of which at least of 1% and not over 2% is a lithium salt;the hydroxyl content being at least stoichiometrically equal to thelithium ion content; the content of the .alkali metal other than lithiumbeing equal in weight to at least /5 of the lithium salt and not overtwice the lithium salt; and heating the surface of the steel to reactthe steel and salts in absence of a solvent, said reaction beingconducted at approximately 800 F.

12. A solution for treating steel at an elevated reaction temperature inabsence of a solvent; said solution comprising a hydroxyl-containingsolution comprising a lithium salt and the salt of an alkali metal otherthan lithium; any nonhydroxyl anions present being members of the classconsisting of acetates, nitrates, and nitrites; said solution containingnot over 10% of solid salts of which at least of 1% and not over 2% is alithium salt; the hydroxyl content being at least stoichiometricallyequal to the lithium ion content; the content of the alkali metal otherthan lithium being equal in weight to at least of the lithium salt andnot over twice the lithium salt.

13. A solution for treating steel at an elevated reaction temperature inabsence of a solvent; said solution comprising a. hydroxyl-containingsolution comprising a lithium salt and the salt of an alkali metal otherthan lithium; any nonsaid solution comprising a hydroxyl-containingsolution comprising a lithium salt and the salt or an alkali metal otherthan lithium; any nonhydroxyl anions present being nitrates: saidsolution containing not over 10% of solid salts of which at least of 1%and not over 2% is a lithium salt; the hydroxyl content being at leaststoichiometrically equal to the lithium ion content; the content of thealkali metal other than lithium being equal in weight to at least of thelithium salt and not over twice the lithium salt. 15. A solution fortreating steel at anelevated reaction temperature in' absence of asolvent;

said solution comprising a hydroxyl-contalning solution comprising alithium salt and the salt of an alkali metal other than lithium; anynonl hydroxyl anions present being nitrites; said solution containingnot over 10% of solid salts of which at least of 1% and not over 2% is alithium salt; the hydroxyl content being at least stoichiometricallyequal to the lithium ion content; the content of the alkali metal otherthan lithium being equal in weight to at least A, of the lithium saltand not over twice the lithium salt.

CLARENCE E. MANGE.

